In the conventional slim electronic apparatuses as shown in FIG. 3, a substrate 3 on which heat generating components 2 such as semiconductors and a CPU are mounted is disposed in a slim electronic apparatus. The heat produced by components 2 travels through heat conductive member 4 such as an aluminum plate, and is discharged outside the apparatus. The discharged heat amount is calculated with the following expression. EQU Q out.varies..SIGMA.(Tsi-Ta).times.Si
where: PA1 (a) a housing having openings; PA1 (b) substrates installed in the housing; PA1 (c) heat generating components mounted on the substrates; PA1 (d) a heat-conductive member thermally coupled to the heat generating components; PA1 (e) a frame thermally coupled to an edge of the heat-conductive member; and PA1 (f) a cooling fan motor housed by the frame and disposed on one of the substrates.
Q out=discharged heat amount PA2 Tsi=a temperature at an "i"th cell of the housing surface, which is finely divided into cells PA2 Si=an area of the "i"th cell PA2 Ta=outer temperature
Accordingly, the housing temperature rises and an area of high temperature increases at greater build-up heat amounts produced by the components.
When this structure is employed in an electronic apparatus such as a mobile computer or a digital video camera, the interior build-up heat could potentially damage its internal electronic operating components. Further, since these apparatus are held in a user's hand during operation, the temperature rise on the housing surface makes the user uncomfortable. Therefore, it has been proposed to discharge the interior build-up heat forcibly outside the apparatus by providing a cooling fan in the apparatus.
FIG. 4 shows another electronic apparatus with a conventional cooling fan. In FIG. 4, substrate 3 accommodating heat generating components 2 such as semiconductors is mounted in housing 1. Substrate 3 mounted at the bottom of housing 1 is shortened at its end in order to provide a space between substrate 3 and a side of the housing. In this space, flat cooling-fan 5 is disposed so that its shortest side extends in the height direction of the apparatus. The heat produced by components 2 travels to fan 5 via heat conductive member 4 made of e.g. aluminum or copper. Then fan 5 forcibly discharges the heat outside the apparatus.
The structure shown in FIG. 4 is employed in a large number of slim notebook-type personal computers. In addition to ensuring reliability of the personal computers, it is desirable that the height of cooling fan 5 be as low as ca. 7.5 mm so that the total housing height thereof should be less than 20 mm.
However, this structure shown in FIG. 4 still has the following problem. Two sheets of double sided substrates accommodate the components. Each substrate measures 50 mm.times.100 mm. The total component mounting area is thus 50 mm.times.100 mm.times.2 sides.times.2 sheets=20000 m.sup.2.
In order to place fan 5 that measures 40 mm.times.40 mm, substrate 3 should be cut out, which reduces the component mounting area by 40 mm.times.40 mm.times.2 sides=3200 mm.sup.2. As a result, the total component mounting area is reduced by 16%.
This area reduction decreases the number of components which can to be mounted, and has been an obstacle to realizing compact size electronic apparatus having high performance and versatile functions.